Elevator system

ABSTRACT

An elevator system for use within a multiple story building includes a car and a counterweight suspended by cables on opposite sides of pulleys supported within the upper end of an elevator shaft. Upper chambers within the car and the counterweight receive a weight medium operable to be transferred between the chambers to vary the weight of the car and the counterweight in relation to changes in the loaded weight of the car. A motor operable in response to changes in the weight of the load automatically moves the weight medium between the counterweight and the car in an amount equal to half the change in the weight of the load to keep the weight of the car and the counterweight balanced so as to reduce the power required to move the car between floors within the building.

1 Nov. 5, 1974 United States Patent 1191 Johnson 1 1 ELEVATOR SYSTEM Primary Examiner-Richard A. Schacher Assistant Examiner-James L. Rowland ll 1461 [76] lnvem'or 3:52:2 i i z m Attorney, Agent, or Firm-Wolfe, Hubbard, Leydig, 1 y & OSann, [22] Filed: June 13, 1973 ABSTRACT [21] Appl 369513 An elevator system for use within a multiple story building includes a car and a counterweight suspended by cables on opposite sides of pulleys supported within the upper end of an elevator shaft. Upper chambers within the car and the counterweight receive a weight medium operable to be transferred between the chambers to vary the weight of the car and the counterweight in relation to changes in the loaded weight of the car. A motor operable in response to changes in [56] References Cited the weight of the load automatically moves the weight UNlTED STATES PATENTS medium between the counterweight and the car in an amount equal to half the change in the weight of the load to keep the weight of the car and the counterweight balanced so as to reduce the power required to move the car between floors within the building.

646918 4/1900 Reyno1ds..... 720,487 2/1903 Roney.....,.... 1,197,529 9/1916 Mil1er......,... 1,216,546 2/1917 Caldwell...... 1 676 161 7/1928 Schiller et a1 3,738,455 6/1973 9 Claims, 10 Drawing Figures sensors PMENTEUHDV 5 i914 1 ELEVATOR SYSTEM BACKGROUND OF THE INVENTION between a chamber in the car and a chamber in the counterweight as the car is loaded and unloaded to maintain a weight relationship between the weight of the car and the weight of the counterweight. An elevator system of this general type is disclosed in Marvin US. Pat. No. 182,280.

SUMMARY OF THE INVENTION changes in the weight of the load within the car so the counterweight and loaded car are kept balanced thereby enabling a low power drive unit to be used to move the car vertically within the elevator shaft.

A more detailed object is to achieve the foregoing by sensing changes in the weight of the load on the floor of the elevator car and automatically transferring the weight medium between the chambers in an amount equal to half the weight change in the load so the weight of the counterweight is adjusted to equal the weight of the loaded car.

The invention also resides in the novel arrangement for sensing changes in the weight of the load and transferring the weight medium between the chambers, in the provision of a unique safety system within the elevator system to keep the car from falling in the elevator shaft and in the novel manner in which the elevator system is supported within the shaft.

These and other objects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS tion.

FIG. 6 is a fragmentary, exploded perspective view of parts of the elevator system.

FIG. 7 is a diagram schematically showing the electrical circuitry used in conjunction with the transfer of the weight medium in the elevator system.

FIG. 8 is a fragmentary perspective view similar to FIG. but showing an alternative embodiment of the invention.

FIG. 9 is a fragmentary side elevational view of the second embodiment of the invention.

FIG. 10 is a diagram schematically showing the electrical circuitry used in conjunction with the transfer of the weight medium in the alternative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings for purposes of illustration, the present invention is embodied in an elevator system particularly adapted for use in a multiple story building of moderate height such as a building containing from two to eight stories. The elevator system includes a car 21 suspended within an elevator shaft 23 located within the building by flexible support lines or main cables 24. As shown in FIG. 5, two of the cables 24 are attached to the car adjacent opposite sides thereof and each cable includes an upper section 25 having one end 26 connected to a cross member 27 secured to the top of the car and an opposite end 29 connected to an upper member 30 secured tothe top of a counterweight 31 so as to suspend the counterweight laterally of the car and within the elevator shaft. A lower section 33 (FIG. 1) of each cable is attached similarly between a lower cross member 34 secured to the bottom of the car and a lower member 35 fastened to the bottom of the counterweight.

As shown in FIGS. 1 and 5, the upper sections 25 of each cable 24 are trained around a set of pulleys 36 mounted rotatably within the upper end of the elevator shaft 23 on a rod 37 extending between theside walls 39 of the shaft (see FIG. 4). The lower sections 33 of the cables similarly are trained around a setof lower pulleys 40 mounted upon a rotatable rod 41 journaled between two upstanding brackets 43 secured to the bottom 44 of the shaft (see FIGS. .1 and 2). Two friction brakes 42 mounted opposite each other adjacent the brackets are utilized to keep the car from falling within the elevator shaft.

One of the more detailed features of the present invention contemplates the provision of a supplemental braking system 45 suitable to prevent the car 21 from falling within the elevator shaft 23 in the event of a failure of the main cables 24 of the brakes 42. To this end, a second set of two cables 46 (see FIGS. 1 and 5) also supports the car within the elevator shaft. Each of the additional cables includes one end 47 which is attached to the upper cross member 27 and opposite end 49 secured to the lower cross member 34 of the car. The intermediate portions 50of the cables are trained around a second set of upper and lower pulleys 51 and 53 2) journaled between brackets 56 which are secured to the bottom 44 of the shaft. As shown in FIG. 2, two friction brakes 57 mounted adjacent the brackets serve to prevent the car from falling within the shaft should the main cables 24 fail.

Supporting the car 21 and the counterweight 31 within the elevator shaft 23 is scaffolding 59 (FIGS. 1 and 6) which includes four T-shaped rails 60 serving to guide the car and the counterweight as they move vertically within the shaft. Herein, two of the rails are spaced from each other adjacent each side wall 39 of the elevator shaft, the two rails each being paired with and facing one of the other rails mounted along the opposite side of the elevator shaft (see FIG. 4). The counterweight is positioned between the two rails located toward the back wall 61 of the elevator shaft while the car is positioned between the two rails located adjacent the front 63 of the shaft. As shown in FIG. 5, the upper and lower cross members 27, 34, 30 and 35 on both the car and the counterweight, respectively, include notched shoes 64 at their opposite ends and the shoes receive inwardly extending flanges 65 of the rails so the counterweight and the car are guided vertically and held against lateral movement within the elevator shaft by the rails.

Advantageously, the scaffolding 59 of the present elevator system comprises a plurality of selected length units 66 and standard length units 67 so as to enable the scaffolding to be assembled easily within the elevator shaft 23. In the assembled scaffolding, the shorter selected length units are located at positions spaced from each other from the top to the bottom of the shaft with one of the standard length units being sandwiched between each two selected length units (see FIGS. 1 and 6). More particularly, each of the scaffolding units 66 and 67 includes tubular vertical members 69 (FIG. 6) at each corner of the unit and horizontal members 70 which parallel the .walls of the elevator shaft and extend between the vertical members to hold the latter together as a unit. Sections of the guide rails 60 are secured to the horizontal members in each unit, the length of the sections of guide rail being such as to abut the ends of the sections of guide rails in the adjacent upper and lower scaffolding units. Preferably, the upper end of each of the vertical members in each scaffolding unit forms a male fitting 71 adapted to fit telescopically within a female fitting 73 in the lower end of each of the vertical members of the next upper scaffolding unit. Turrlbuckles 74 braced between the vertical corner members 69 and the side walls 39 and 61 (FIGS. 3 and 6) hold the scaffolding units 66 and 67 against lateral movement within the elevator shaft.

The standard length scaffolding units 67 extend generally between each floor 75 in the building and the overlying ceiling 76 (see FIG. 1) and. more particularly. are of a length approximately equal to the height of an elevator door opening 77 on each floor so they may be easily inserted into the elevator shaft 23 when assembling the scaffolding 59. Each of the selected length scaffolding units 66 are of a height so as to extend upwardly from the upper end of the next adjacent lower standard length unit to a position generally horizontal with the bottom of the next upper door opening. By virtue of this arrangement, the scaffolding may be adapted to fit within any length of elevator shaft regardless of the spacing between the top of the door opening and the overlying floor by simply using different heights of selected length units when assemblying the scaffolding. Moreover, assembly of the scaffolding within the shaft is accomplished in a relatively easy manner by inserting a first selected length unit into the elevator shaft and then mounting a standard length unit on top of the selected length unit, the process being repeated for each floor in the elevator shaft.

For movement of the car 21 vertically within the scaffolding 59 of the elevator system 20, a weight medium 79 (FIG. 5) such as a liquid is transferred between a chamber 80 in the car and a corresponding chamber 81 in the counterweight 31 to maintain a predetermined weight relationship between the weight of the car and the weight of the counterweight. In accordance with the primary aspect of the present invention, the elevator system 20 includes means movable automatically in response to changes in the load to move the weight medium between the car and the counterweight so the loaded weight of the car including the weight of the weight medium in the car equals the weight of the counterweight plus the weight of the weight medium in the counterweight thereby enabling use of a low power drive unit 83 (FIG. 6) to move the car between the floors in the building. For this purpose, the automatically movable means includes a motor 85 (FIG. 5) which is actuated automatically in response to changes in the weight of the load in the car to move an amount of the weight medium proportional to the change in the weight of the load between the chambers in the car and the counterweight to equalize the weight of the car and the counterweight so that the elevator system is balanced. Advantageously this enables a small motor 86 (FIG. 6) to be used in the power drive unit to move the car vertically within the elevator shaft.

In the present instance, the motor 86 for moving the car 21 vertically within the elevator shaft 23 is mounted adjacent the bottom 44 of the shaft (see FIG. 6) and connected by a chain 87 to the rod 41 supporting the lower set of pulleys 40 so as to drive the main cables 24 of the elevator system 20. A conventional control system (not shown) is used to actuate and deactuate the motor 86 to move the elevator car within the shaft and is operated from within the elevator car on a control panel 86 (see FIG. I) mounted on one wall within the car. The motor 85 is actuated automatically to move the weight medium 79 between the chambers 80 and 81 as the change in the weight of the load occurs, the entire transfer of the medium occurring during the time interval provided by the control system for holding the elevator door 90 (FIG. 1) open as the car rests at a floor. Once the door is closed, the motor 85 is prevented from being actuated to move the weight medium between the chambers. Accordingly, the motor 85 is kept from being actuated as a result of apparent changes in the weight of the load caused by the acceleration or deceleration of the car 21 within the elevator shaft 23.

In the exemplary form of the invention illustrated in FIGS. 1 through 7, the chambers 80 and 81 are mounted on the tops of the car 21 and counterweight 31, respectively, and each is closed liquid-tight, having side walls 82, a top wall 84 and a bottom wall 88. A hose 91 (FIG. 5) communicates between the two chambers through the top walls 84 and is trained around a wheel 92 secured to the rod 37 supporting the main upper pulleys 36. Herein, the motor 85 provided for moving the weight medium or liquid 79 through the hose between the two chambers is a three phase alternating current induction motor and is mounted within the chamber 80 on the top of the car. More particularly, the motor is included as part of a constant displacement reversible pump 93 which serves to move the liquid either from the car chamber 80 to the counterweight chamber 81 when the load within the car is increased or to move the liquid from the counterweight chamber to the car chamber when the load in the car is decreased.

To control automatically the amount of the liquid 79 transferred between the chambers 80 and 81, means are provided for creating a voltage signal E (HO. 7) whose value is proportional to the weight of the load within the car 21. In response to changes in the value of the signal E,,, the constant displacement pump 93 is actuated to begin transferring a predetermined amount of the liquid between the car and the counterweight 31 with each revolution of the pump. The signal E is then algebraically summed with a feedback signal Ep whose value is modified as a function of twice the amount of liquid transferred between the car and the counterweight. lf twice the weight of liquid within the counterweight as represented by the feedback signal E does not agree with the weight of the load within the car represented by the signal E,,, the pump continues to operate until the total weight of the car equals the total weight of the counterweight.

One arrangement for achieving the foregoing is shown very schematically and in elementary form in FIG. 7, it being understood that this representation is simply for the purpose of explaining the fundamental principles involved. The signal E representativeof the weight of the load within the car 21 takes the form of a voltage which is produced as a spring-supported false floor 94 (also see FIG. 5) within the car moves vertically when the weight of the load is increased or decreased'Attached to one edge of the false floor is a vertically extending rack 95 which engages a pinion 96 fixed to a wiper arm 97 adaptedto move across a potentiometer 99. As changes in the weight of the load move the false floor vertically within the car, the wiper arm moves across the potentiometer. The latter is connected across power lines L-l and L-2 which are energized by a source of direct current, the upper and lower ends of the potentiometer being connected to the positive and negative lines L-l and L-2, respectively. As the weight of the load increases or decreases, the wiper arm moves upwardly or downwardly along the potentiometer so that the voltage E between the lines is increased or decreased. When there is no load on the false floor of the car, the magnitude of the voltage 13,,

is zero. 1

The feedback signal E, is produced by second means in the form of a wiper arm 100 (HO. 7) which is coupled to a drive shaft 101 of the pump motor 85 through reduction gearing 103 to move across a potentiometer 104 connected between the power lines L-l and L-2. The wiper arm 100 moves toward the upper end of the potentiometer to increase the value of the feedback signal E when the liquid 79 is being pumped from the car chamber 80 into the counterweight chamber 79 and moves toward the lower end of the potentiometer 104 to decrease the value of the feedback signal Ep when the liquid is being pumped from the counterweight chamber to the car chamberh To actuate the motor 85 so that the liquid 79 is pumped in the proper direction between the chambers 79 and 80 as the weight of the load either is increased or decreased, a sensitive polarized relay R1 is connected between the two potentiometers 99 and 104. The signal E is transmitted in one direction by a conductor 105 connected to one end of the polarized relay and the feedback signal E is transmitted in the opposite direction to the other end of the relay by a conductor 106. The polarized relay in effect sums the two opposing signals E and E and moves in the direction dictated by the greater signal to actuate the motor so the liquid is pumped in the appropriate direction between the two chambers according to whether the load is increased or decreased in weight. When the weight of the load is increased, the voltage of the signal E becomes larger than the voltage of the feedback signal E and a signal E resulting from the sum of the signals E and E, flows through the polarized relay R1 in a direction indicated by the dashed arrow A so as to close a switch Rla. This in turn actuates a relay R2 to close switches R2a, R212 and R2c thereby energizing the motor 8510 pump the liquid from the car 21 and to the counterweight 31.

Herein, the switches R2a and R21; are located within power lines L-3 and L 1, respectively, which are connected to the motor and are energized by a three phase alternating current voltage source, the switch R20 being located within a ground line L-5 leading from the motor. When the current from the A.C. source flows through the power lines L-3 and L-4, the motor shaft 101 turns in the direction indicated by the dashed arrow C so the wiper arm 100 is moved toward the upper end of the potentiometer 104 a predetermined distance in relation to the weight of the liquid being transferred so the voltage of the signal E increases, decreasing the value of the signal E The relation between the weight of the liquid being transferred and'the resulting movement of the wiper arm 104 is such that the voltage of the feedback signal E, approaches the voltage of the signal E,, as the twice the weight of the liquid transferred to the counterweight approaches the weight of the load within the car. Once the voltages of the signals E and E, are equal, the voltage of the signal E becomes zero causing the relay Rl to center so switch R1a opens to drop out relay R2 which in turn causes the switches R2a, R2b and R2c to open thereby de-energizing the motor.

If the weight of the load in the car 21 is decreased, the wiper arm 97 moves back toward the lower end of the potentiometer99 decreasing the voltage of the signal E below the value of the signal E so that the signal E flows through the relay R1 in a reverse direction indicated by the arrow B so as to cause a switch Rlb to close. As a result, a relay R3 is energized to close switches R3a, R3b and R30 which are located in conductors 107, 108 and 109, respectively. The latter conductor is connected in the line L-S around the switch R2c and the conductors 107 and 108 by-pass switches R20 and R212 cross connecting the power lines L-3 and L-4 to effect a reverse connection of the lines L-3 and L-4 with the motor so the latter is energized to turn in a reverse direction as indicated by the arrow D in F IG. '7. Accordingly, the pump 93idraws the liquid 79 through the hose 91 from the counterweight chamber 81 and into the car chamber 80. With the motor shaft 101 turning in the reverse direction, the wiper arm is swung toward the lower end of the potentiometer 104 until the voltage of signal E, again equals the voltage of signal E,,. At this point, the relay R1 centers and the switch Rlb opens de-energizing the relay R3 which in turn opens the switches R3a, R3b, and R30 to stop the motor, the weight of the car and the weight of the counterweight again being equal so the elevator system is balanced.

To keep the motor 85 from being actuated when the apparent weight of the load increases and decreases from the acceleration and deceleration of the car 21 within the elevator shaft 23, a switch S1 in the circuit normally is open when the elevator door 90 is closed to keep either relay R2 or R3 from being energized should the signal E flow in one direction or the other through the relay R1. In addition, to prevent the motor from being actuated when insufficient liquid 79 is available to be pumped between the chambers 80 and 81 as a result of liquid being lost from the system, a switch S2 is provided in the circuit and normally is closed when sufficient liquid is within the system to be pumped. But, when the liquid in the system, as measured by floats (not shown) in the chambers 80 and 81, becomes too low to supply the demand of the liquid to be transferred as required by the load change within the car, then the switch S1 is opened to de-energize either the R2 or R3 relays and as a result deactuate the motor.

Another form of the invention is illustrated in FIGS. 8, 9 and 10 in which parts corresponding to the parts of the first embodiment are indicated by the same primed reference numerals. In this form of the invention, the weight medium 79' is a non-kinking chain which is coated with a sound deadening material (not shown) such as plastic and which is of a predetermined weight per unit of length. An intermediate portion of the chain 79 is trained over a sprocket 112 at the upper end of the elevator shaft 23' and extends between the two chambers 80 and 81' both of which are open at their upper ends to permit passage of the chain. An excess length of the chain, corresponding in weight to one-half the load capacity of the elevator system 20' plus each additional length whose weight produces a desired safety factor for overload capacity, normally is stored in the car chamber 80 under a no load condition in the car 21'. To balance the weights of the car and the counterweight 31 when the car is loaded, a portion of the excess length of chain equal to one-half the weight of the load within the car is transferred from the car chamber and is accumulated in the counterweight chamber.

To offset the weight of the length of chain 79 extending between the two chambers 80 and 81, an added length of chain 111 is suspended within the lower end portion of the elevator shaft 23 between the car 21 and the counterweight 31. The intermediate portion of this length of chain is trained around a lower sprocket 113 which is fixed on the rod 41' supporting the main cables 24' of the elevator system 20'.

For movement of the chain 79' between the two chambers 80 and 81, the sprocket 112 is connected to the rod 37' by way of a clutch 114 which serves to permit the sprocket to rotate freely on the rod as the chain is being transferred between the car 21 and the counterweight 31 Herein, the motor 85 used to move the chain between the chambers is mounted on the back wall 61' of the elevator shaft 23 adjacent the upper end thereof. A clutch and pulley 115 connected between the motor shaft 101 and the sprocket 112 serves to transmit the rotational power of the motor to the sprocket thereby rotating the latter on the rod to move the chain. During movement of the car within the elevator shaft, the clutch and pulley 115 is disengaged while the clutch 114 is engaged to hold the sprocket for movement with the rod. Accordingly, the motor shaft is kept from rotating as the rod rotates during movement of the car. Conversely, when the chain is being transferred between the chambers and 81, the clutch and pulley 115 is engaged and the clutch 114 is disengaged to permit the sprocket to be rotated freely on the rod by the motor.

The circuitry for operating this embodiment of the invention is illustrated schematically in FIG. 10 and is similar to the circuitry of the first described embodiment of the invention and thus need not be described in detail. As in the first circuit, the present circuit includes the sensitive polarized relay R1 and the two potentiometers 99' and 104', the potentiometer 99' serving to indicate the weight of the load within the car 21 and the potentiometer 104 producing the feedback E to center the relay R1 when equal with the signal 15,, so the motor is deactuated when the amount of chain 79' transferred between the chambers 80' and 81 in the car and the counterweight, respectively, equals one-half the change in the weight of the load. Herein, the motor is connected directly to the chain sprocket 112 through the clutch 115 which is engaged upon energization of a coil 116 in the circuit as either switch Rla' or Rlb is closed when the polarized relay R1 shifts off center. At the same time, a second clutch coil 117 also is energized to disengage the clutch 114 so the sprocket is free to turn relative to the rod 37. The directions of the arrows C and D indicate the directions in which the reversible motor 85' will be driven to either add weight to the chamber 81 within the counterweight 31 or to remove weight from the counterweight as current either flows from the potentiometer 104 to the potentiometer 99 with a load increase or from the potentiometer 99 to the potentiometer 104' with a load decrease.

Thus, it is seen from the foregoing that, the elevator system 20 of the present invention requires less power to operate, is easier to install and, accordingly, is less expensive to own and operate. Primarily, this is because the motor 85 is actuated automatically in response to changes in the weight of the load within the car 21 to transfer the weight medium 79 between the car and the counterweight 31 in order to keep the system balanced so the power required to move the car between floors in the building is provided easily by the small motor 83.

I claim:

1. An elevator system for use within a vertical shaft in a multiple story building including, a car ofpredetermined unloaded weight suspended within the shaft to transport a load between floors within the building, a counterweight suspended within the shaft and spaced laterally from said car to offset the unloaded weight of the car, a set of upper and lower wheels rotatably mounted adjacent the upper and lower ends of the shaft, respectively, a flexible support line trained around said upper and lower wheels, said car and said counterweight being fastened to opposite sides of said line between said upper and lower wheels, a small motor operable to power rotate one of said wheels in said set to drive said line around said wheels to move the car and said counterweight vertically within said shaft, a weight medium movable between said counterweight and said car to vary the weight of the counterweight in relation to changes in the weight of the load in the car, means mounted within said car and operable to produce a signal in response to changes in the load, and means operable in response to said signal to move said weight medium between said counterweight and said car in an amount equal to half the change in the weight of the load to keep the weight of the medium in the counterweight substantially equal to the weight of the load plus the weight of the medium in the car prior to movement of said car whereby the system is kept balanced to reduce the power required of said small motor to move the car between floors.

2. An elevator system as defined by claim 1 wherein said means operable to move the weight medium includes a motor adapted to be actuated in response to said signal to move said weight medium between said counterweight and said car, second means operable to produce a second signal to deactuate said motor automatically when the amount of weight medium moved equals one-half the weight of the change in the load.

3. An elevator system as defined in claim 2 wherein said weight medium is liquid, said car including a first chamber formed therein to hold said liquid, a second similar chamber formed within said counterweight, a hose connected between said chambers and through which said liquid may be moved from one chamber to the other, a pump mounted within one of said chambers and operable by said signal-responsive motor to move said liquid through said hose.

4. An elevator system as defined by claim 2 wherein said weight medium is a chain, said system further including a sprocket rotatably mounted in the shaft adjacent the upper end thereof, said chain extending between said car and said counterweight and being trained around said sprocket, said signal-responsive motor being connected to said sprocket to power rotate the latter to move said chain between said counterweight and said car, aclutch connected between said sprocket and said motor and operable to permit said sprocket to free wheel as said car is moved vertically within said shaft.

5, An elevator system as defined by claim 4 wherein said chain is coated with a sound deadening material.

6. An elevator system as defined by claim 1 including scaffolding mounted within said shaft to support said car and said counterweight against lateral movement within said shaft, said scaffolding comprising a plurality of first units of selected length spaced from each other within said shaft and extending from the top to the bottom thereof, a plurality of second units of standard scaffolding units including vertically extending guide rail sections along opposite sides thereof to guide said car and said counterweight vertically within said shaft.

8. An elevator system as defined by claim 1 including a first brake means connected to one of said wheels in said set and operable to prevent free fall of said car within the shaft, a second set of upper and lower wheels rotatably mounted adjacent the upper and lower ends of the shaft, respectively, a second flexible support line having one end connected to the top of said car, an intermediate portion trained around the upper and lower wheels of said second set and an opposite end portion connected to the bottom of said car, a second brake means connected to one of the wheels in said second car and operable to prevent free fall of said car within the shaft.

9. An elevator system for use within a vertical shaft in a multiple story building including, a car of predetermined unloaded weight suspended within the shaft to transport a load between floors within a building, a counterweight suspended within the shaft and spaced laterally from said car to offset the unloaded weight of the car, means connected between said car and said counterweight and supporting said car and said counterweightwithin the shaft, a first motor for moving said car vertically within the shaft between floors, a first chamber, a second chamber within said counterweight, a weight medium contained within said first chamber, connected with said second chamber and movable be tween said counterweight and said car to vary the weight of the counterweight in relation to changes in the weightof the load in the car, first means mounted within said car and operable automatically to produce a first signal when the weight of the load in the car is changed, a second motor adapted to be actuated in response to said first signal to move said weight medium between said chambers, and second means operable prior to movement of said car to produce a second signal to deactuate said second motor automatically when the amount of weight medium moved causes the weight first motor to move the car between floors.

l l k 

1. An elevator system for use within a vertical shaft in a multiple story building including, a car of predetermined unloaded weight suspended within the shaft to transport a load between floors within the building, a counterweight suspended within the shaft and spaced laterally from said car to offset the unloaded weight of the car, a set of upper and lower wheels rotatably mounted adjacent the upper and lower ends of the shaft, respectively, a flexible support line trained around said upper and lower wheels, said car and said counterweight being fastened to opposite sides of said line between said upper and lower wheels, a small motor operable to power rotate one of said wheels in said set to drive said line around said wheels to move the car and said counterweight vertically within said shaft, a weight medium movable between said counterweight and said car to vary the weight of the counterweight in relation to changes in the weight of the load in the car, means mounted within said car and operable to produce a signal in response to changes in the load, and means operable in response to said signal to move said weight medium between said counterweight and said car in an amount equal to half the change in the weight of the load to keep the weight of the medium in the counterweight substantially equal to the weight of the load plus the weight of the medium in the car prior to movement of said car whereby the system is kept balanced to reduce the power required of said small motor to move the car between floors.
 2. An elevator system as defined by claim 1 wherein said means operable to move the weight medium includes a motor adapted to be actuated in response to said signal to move said weight medium between said counterweight and said car, second means operable to produce a second signal to deactuate said motor automatically when the amount of weight medium moved equals one-half the weight of the change in the load.
 3. An elevator system as defined in claim 2 wherein said weight medium is liquid, said car including a first chamber formed therein to hold said liquid, a second similar chamber formed within said counterweight, a hose connected between said chambers and through which said liquid may be moved from one chamber to the other, a pump mounted within one of said chambers and operable by said signal-responsive motor to move said liquid through said hose.
 4. An elevator system as defined by claim 2 wherein said weight medium is a chain, said system further including a sprocket rotatably mounted in the shaft adjacent the upper end thereof, said chain extending between said car and said counterweight and being trained around said sprocket, said signal-responsive motor being connected to said sprocket to power rotate the latter to move said chain between said counterweight and said car, a clutch connected between said sprocket and said motor and operable to permit said sprocket to free wheel as said car is moved vertically within said shaft.
 5. An elevator system as defined by claim 4 wherein said chain is coated with a sound deadening material.
 6. An elevator system as defined by claim 1 including scaffolding mounted within said shaft to support said cAr and said counterweight against lateral movement within said shaft, said scaffolding comprising a plurality of first units of selected length spaced from each other within said shaft and extending from the top to the bottom thereof, a plurality of second units of standard length sandwiched between said first units, one of aid second units extending generally between each floor and its overlying ceiling.
 7. An elevator system as defined by claim 6 including means for supporting each of said scaffolding units within said shaft against lateral movement, each of said scaffolding units including vertically extending guide rail sections along opposite sides thereof to guide said car and said counterweight vertically within said shaft.
 8. An elevator system as defined by claim 1 including a first brake means connected to one of said wheels in said set and operable to prevent free fall of said car within the shaft, a second set of upper and lower wheels rotatably mounted adjacent the upper and lower ends of the shaft, respectively, a second flexible support line having one end connected to the top of said car, an intermediate portion trained around the upper and lower wheels of said second set and an opposite end portion connected to the bottom of said car, a second brake means connected to one of the wheels in said second car and operable to prevent free fall of said car within the shaft.
 9. An elevator system for use within a vertical shaft in a multiple story building including, a car of predetermined unloaded weight suspended within the shaft to transport a load between floors within a building, a counterweight suspended within the shaft and spaced laterally from said car to offset the unloaded weight of the car, means connected between said car and said counterweight and supporting said car and said counterweight within the shaft, a first motor for moving said car vertically within the shaft between floors, a first chamber, a second chamber within said counterweight, a weight medium contained within said first chamber, connected with said second chamber and movable between said counterweight and said car to vary the weight of the counterweight in relation to changes in the weight of the load in the car, first means mounted within said car and operable automatically to produce a first signal when the weight of the load in the car is changed, a second motor adapted to be actuated in response to said first signal to move said weight medium between said chambers, and second means operable prior to movement of said car to produce a second signal to deactuate said second motor automatically when the amount of weight medium moved causes the weight of the counterweight to balance with the loaded weight of the car so as to reduce the power required of said first motor to move the car between floors. 